Current fluid actuator assemblies used in telescopic devices are bulky and heavy. There are several telescopic devices designed trying to solve such problems. Prior art telescopic devices are also slow and labour intensive to extend.
U.S. Pat. No. 3,804,262 shows a telescopic device of a mobile crane having telescopic hollow boom sections, in which there are arranged a respective hydraulic actuator for propulsion of the boom sections for extension and retraction.
U.S. Pat. No. 5,628,416 shows a telescopic device of a mobile crane having telescopic boom members and a single stage piston and cylinder unit and locking bolts for coupling each boom member to the actuator unit for extension and retraction.
U.S. Pat. No. 5,632,395 shows a telescopic device of a mobile telescopic crane having a multistage simple-acting piston-cylinder unit arranged for extending the telescopic crane. A steel rope is provided for retracting the telescopic crane.